Suspended excess potential drain



Jan. 26, 1932. c. E. BENNETT SUSPENbED EXCESS POTENTIAL DRAIN Filed June 19. 1928 5 Sheets-Sheet 1 INVENTOR CHARLES E. BENNETT @222: aizarrzqys Jan. 26, 1932. c. E. BENNETT SUSPENDED EXCESS POTENTIAL DRAIN 5 Sheets-Sheet 2 Filed June. 19

INVENTOR CHARLES E. BENNETT Zy 222's ail-drag:

Jan. 26, 1932. c. E. BENNETT SUSPENDED ExcEss POTENTIAL DRAIN Filed June 19, 1928 3 Sheets-Sheet 3 INVENTOR CHARLESEBENNETT 23/ his aZZorne /s Patented Jan. 26, 1932 PATENT OFFICE CHARLES E. BENNETT, OF DECATUR, GEORGIA SUSPENDED EXCESS EOTENTIAL DRAIN Application filed June 19,

' This invention relates to devices for the protection of high tension power transmission lines and of power stations in'sucli lines. It is customary in such lines to insulate the line conductors from their supports, the insulators-being designed to prevent flashing over, with consequent loss of power, under normal conditions or even under certain abnormal conditions. where the normal potential of the line is not greatly exceeded. Such are ordinary conditions. 'It is not practicable however to in'sulate the line conductors to such an extent thatexcess of potential, or superpotential as it is called, due generally to lightning discharge could not be drained away to ground. Superpotential drains are therefore provided at various points along the transmission line to relieve the line of this excess potential caused by lightning discharge. If

the substations or power stations are less capable of withstanding an excess potential on their equipment than the lines leading thereto, the protecting drains are placed near the stations on the conductors feeding thereto or receiving power therefrom. If the line conductors and the line'equipment are less capable of withstanding superpotential, the drains are located along the line in such number as conditions require.

In general, an excess potential drain consists of an arcing gap and an interrupter. A common practice-heretofore has been to support the terminals of the gap on the pole or as tower structure which carries the line conductor. The interrupter in such arrangements has been separately supported on the tower and'connected between one terminal of the are gap and ground, the other terminal 4 of the gap being connected to the conductor.

g The interrupter is a device which normally .establishes aconnection to ground but which will break that connection after relief of excess potential therethrough. Otherwise, once an arc was established across the gap and the excess potential was relieved, the line conductor would remain grounded. In some interrupters there is provision for reestab- 1928. Serial No. 286,650.

one pole of the gap and ground. As the word interrupter is used here, it includes both types. By ground of course, is meant any object at substantially earth potential.

The preferred interrupter is of the electrolytic type in which the excess potential is relieved by discharge to ground through a volatile electrolyte, after which the electrolyte rcestablishes the connection to the arc gap. Such an interrupter is shown here and conforms to that of my application for patent, Serial Number 187,310 filed September 23, 1926. I prefer that type, because, in it, the interruption of the are occurs within one or two cycles and because, as a structure, it has desirable characteristics of flexibility, strength and ease of manufacture, installation and replacement.

According to the present invention, in its preferred form, I propose to suspend the superpotential drain device between the line conductor and the earth or the lower end of the tower or pole which carries the line conductor. The conductor is suspended by a string of insulators and the drain device is attached at is upper end to the conductor itself or preferably to the lower end of the insulator string and in line therewith. In either case, the drain device is suspended from the string of insulators which support the line conductor and insulate it from ground.

The drain device may be arranged with the means forming the arc gap 011 the line side of the interrupter or on the ground side. lVhen on the line side, the gap is best formed by an insulating body which may consist of a string of units, as in the case of the line insulation mentioned above, and which has poles or arcing terminals at its ends. The interrupter is then suspended from the lower end of this insulating body.

Whether the arc gap is on the line side or on the ground side of the interrupter, its insulating strength is less than that of the line insulation so that the discharge of excess potential in the line will be by way of the drain device rather than over the line insulation. It is understood that the description of the drain device as being suspended from the line supporting and insulating means does not require, although it includes, a free suspension since it generally is desirable to give the lower end of the drain device lateral support at least. Vith the type of interrupter which I prefer to use, it is bestto support the lower tank from the earth or from the lower end of the line carrying tower in order to prevent stain on the tubes.

It is an object of the invention therefore to protect transmission line and power house equipment by providing at the points needing protection a connection to ground including an interrupter and an insulating medium of less strength than the regular line insulation between the conductors and their supports.

It is a further object to provide a way of suspending the drain device so that it will be easily installed, will not be hazardous and will be efficient in its operation.

The present preferred construction is described hereinafter and is illustrated in the accompanying drawings. In the drawings Figure 1 is an elevation view of a transmission line support showing .interrupters installed according'to this invention;

Figure 2 is a profileiview of the same, and Figure 3 is a more detailedview of the suspensiontype of connection between the drain and the line; 7

Figures 4 and 5 are views of modifications .in which the arc gap is on the ground side of the interrupter.

The construction is shown .in a three-wire transmission line, with a similar arrangement for-each wire, as in Fig. 1. 'The conductors Aare suspended from a cross arm 2 supported on poles 3 or other usual line carrying structures. Braces i give rigidity and strength to the supporting structure. The suspension of the conductors is by insulators B .of any-suitable type connected to thecrossbars at points spaced from the verticalsupports 3 in the known manner to insulate the conductors from the supports in all directions. Below each conductor is a super- ,potential drain consisting of an insulating body C forming an arc gap and an interrupter D of thetype shown in my co-pending application referred to above. This body C is of less insulating strength than the insulation B between the line conductor and the cross support 2. The terminals 8, 9 at the ends of the insulator C may he of the horn or ring type or of any suitable construction to .permitan arc to bridge the insulatingbody C-without following the surface of the insu lators.

Referring to Fig. 3 in which there is a more detailed view, it Wlll be seen that the line insulation B (shown broken) is of the How'- lett type and, for instance, may consist of seven units connected to the arm 2 by a bolt serving as acushion.

The conductor A is secured to the insulators by the attaching member 7 and is supported thereby from the cross-arm. The insulating body C is of the same type as B but has fewer units so that its insulating strength is less than that of B, three units being shown in F ig. 3 as a possible number to use where seven are used in the line insulation B. This body C is suspended directly below the insulation B by a conducting link 6 which forms part of the attaching member 7. At the lower end of this link is an arcing ring 8 surrounding the insulators B and at the lower end of the insulators is another ring 9 facing ring 8, the two providing an arcing gap. As shown the ring supports are integral with the links 6 and 11. \Vithout the rings or their equivalents, arcing might take place from link 6 to link 11 and would injure the insulating units therebetween.

To link 11 conductively attached the upper tank 12 of a superpotential drain or interrupter of the electrolytic type. The tank 12 has a gauge 13, vent 14 and a plug 15 which may be removed for the introduction of electrolyte into the tank, all as shownin my copending application Serial No. 137,310. Th insulating tubes 16 are connected to the lower-end of thetank 12 and extend into the lower tank 17 which is connected to ground as at 18. The body of electrolyteis contained in both tanks but does not fill either, the bodies of air above the liquid in the tanks The tubes 16 are of low grade rubber composition so as to be flexible and yieldable but of strength to resist the force of the are and of the volatilization of the liquid. The tubes are longer than the normal arc-over spacing forwhich they are to be used and, by reason of this, the arc is drawn out and broken within the tubes. This and the yieldable characteristic of the tubes give the speedy operation which makes this type of interrupter preferable. It is, however, within the scope of this invention to use other types of interrupter.

, I wish particularlyto call attention to the fact that the arcing rings at the ends of the insulator C have no connection .to ground except through the interrupter. In previous practice the arcing terminalshave been supported on grounded insulating standards which may flash over ahead of the operation of the interrupter and thus cause a serious line short circuit to ground with no provision for its interruption after the excess potential isrelievec By the present arrangement in which the means forming the arcing gap are suspended from themeans by which the conductors are suspended, either by direct connection to this line suspension means or to the conductor itself, and are in contact solely with the conductor and the interrupter, this hazard is avoided.

The operation is as follows.

Assumingan excess of potential in conductor A due to a lightning discharge, there will be a diiference of potential between rings 8 and 9 since tl e latter is grounded through the interrupter. By reason of the greater number of units in insulator B than in C, the difference of potential necessary to cause flash-over at B is greater than at C and the flash-over will occur therefore at C.

The arcing rings prevent the are from following the insulators themselves and if the arc does not play for too long a time, the insulator C will be uninjured. As soon as an arc is established across the rings and the excess is relieved through the electrolyte to ground, the drain connection is broken by volatilization of the electrolyte in tubes 16 due to the heat generated by the discharge, this occurring in one or two cycles in an interrupter of the type shown. The are across 8, 9 will of course be then broken but upon reestablishment of the electrolytic path through the tubes 16, the apparatus will be in position to relieve further excess potential in the line if there is any. The interrupter shown is peculiarly useful in that it interrupts the ground connection in one or two cycles and thus prevents a long continued play of the arc between rings 8 and 9 which might injure the insulators C.

If, by chance, the tubes 16 become defective and a discharge occurs, the tubes will burst and let the electrolyte out breaking the connection and preventing reestablishment of it. The unit is then not a hazard on the line.

The particular way shown in which the excess potential drain is installed in the transmission system has many advantages. It may be added to an existing line with no difficulty. The are gap terminals are in contact solely with parts which are either well insulated from ground or grounded through the connection designed for the relief of excess potential thus avoiding the hazard of short circuits to ground by way of parts not designed for that purpose.

In Figures 4 and 5 are shown modifications in which the means forming the arc gap C are placed on the ground side of the interrupter D. The interrupter D is suspended in the same manner as the insulating body C in'Figures 1, 2 and 3 and, therefore, in these figures, the connection is shown diagrammatically with the line insulation omitted. The insulating body C may be suspended from the lower end of the interrupter and connected to ground by a wire, but where an interrupter of the sort shown here is used, it is preferable to support the insulating body separately, as by the cross member 20 which would be near'the lower end of the tower, to avoid undue tension on the tubes connecting the tanks of the interrupter.

Various modifications of the structures shown are possible all within the scope of the following claims.

1. In a transmission line, a line conductor, insulating and supporting means for the line conductor, supporting and insulating it from ground, means forming an excess p0 tential drain suspended from said supporting and insulating means, said drain comprising an interrupter and an insulating body with arcing terminals at its ends.

2. In a transmission line, a line conductor, means supporting the line conductor and insulating it from ground, means forming an excess potential drain suspended from thev line conductor supporting and insulating means, said drain comprising an interrupter and an insulating body with arcing terminals at its ends, the body being of less insulating strength than the line insulation.

3. In a transmission line, a line conductor, means supporting said conductor and in! sulating it from ground, means forming an excess potential drain for said conductor, said means comprising an insulating body suspended from said first named means, said body having an insulating strength less than said line conductor insulating means, and a conductive connection from said insulating body to ground.

4. Ina transmission line, a line conductor, means supporting said conductor and insulating it from ground, means forming an excess potential drain for said conductor, said means comprising an insulating body su pended from said first named means, said body having an insulating strength less than said line conductor insulating means, and means connected to said body normally establishing a connection to ground, said last mentioned means being adapted to interrupt the ground connection upon discharge therethrough.

5. In a transmission line, a line conductor, means supporting said conductor and insulating it from ground, means forming an excess potential drain for said conductor, said means comprising an insulating body suspended from said first named means, said body having an insulating strength less than said line conductor insulating means, and means connected to said body normally establishing a connection to ground, saidlast mentioned means being adapted to interrupt the ground connection upon discharge therethrough and to reestablish the connection thereafter.

6. In a transmission line, a line conductor, means supporting said conductor and insulating it from ground, means forming an excess potential drain for said conductor, said means comprising an insulating body suspended from said first named means, said body having an insulating strength less than said line conductor insulating means, an arcing pole at each end of said-body, one pole being in conductive connection with the line conductor, and a conductive connection from the other pole to ground.

ground connection fromsaid other pole, said 7. In a transmission line, a line conductor,

aneanssupporting said conductor and insulatingit from ground, means'forming an excess potential drain for said conductor, said means comprising an insulating body suspended from said first named means, said body having an insulating strength less than said line conductor insulating means, an arc- 111g pole at each end of said body, one pole conductively connected with the line conductor and means normally establishing a last mentioned means being adapted to interrupt said connectlon upon discharge therethrough.

8. In a transmission line, a 'line'conducton-means supporting said conductor and insulating'it from ground, meansforming an excess potential drain for said conductor, said means comprising an insulating body suspended from said first named means, said body having an insulating strength less than said line conductor insulating means, an arcing pole at each end of said body, one pole conductively connected with the line conductor and means normally establishing a ground connection from said other pole, saidmeans being adapted to interrupt said connection upon discharge therethrough and to reestablish said connection thereafter.

9. In a transmission hne, a line conductor, .means supporting said conductor and insulating 1t from ground, means forming an excess potential drain forsaid conductor,

said means comprising an insulating body suspended from said first named means, said body having an insulating strength less than said line conductor insulating means, an arcing pole at each end of said body, the upper pole being conductively connected to the line, a tank suspended from said insulating body and in conductive connection with the lower p01e,a second tank there below and connected to ground, a yieldable insulating tube between said tanks and extending into the lower tank, and a body of electrolyte in said tanks and tubes.

10.'In-atransmission system,-a line conductor, means supporting said conductor and insulating 1t from ground, and an excess potential drain, said dram comprising an 1n- .terrupter connected conductively to the line conductor, and a means formmgan arc gap with one; termlnal connected to ground and the other terminal connected to the ground side 01' said interrupter.

* In testimony whereof I have slgned my name to this specification.

CHARLES. E. BENNETT. 

